During the production of fibers for papermaking, wood or another source of fibers is processed into chips and mechanically or chemically treated such that the chips may be broken down further and refined into individual fibers.
High consistency disk refiners are used with stock containing eighteen to sixty percent fiber by weight. High consistency refiners produce mechanical and semichemical pulp or furnish from undigested wood chips and semidigested wood chips. The refiner breaks down wood chips and clumps of wood fibers into individual fibers from which paper may be formed. After processing in a high consistency refiner, the fibers may be further processed in, for example, a low consistency refiner to improve their freeness or bonding capability.
A refiner disk consists of a disk-shaped steel or steel-alloy casting which has a multiplicity of generally radially extending bars integrally cast to extend from the surface of the disk. A first refiner disk is mounted on a rotor for rotation and another disk is held opposed to the first refiner disk, either by rigid mounting or by mounting on an oppositely rotating rotor. The refiner disks, as they move past each other, separate and refine the wood pulp as it passes between the opposed disks.
When dealing with high consistency pulp and wood chips, the edges of the refiner bars act as cutting edges for separating fibers from wood chips or clumps of fibers.
Disc refiners are used in the papermaking industry to prepare the cellulose fibers prior to delivering the pulp to the papermaking machine.
It is the purpose of a stock refiner to modify and separate the fibers without significantly reducing the length or individual strength of these fibers. The action of the refiner requires that the fibers pass through the refiner disks slowly. The energy which is expended to drive the refiner results in the generation of steam between the refiner disks. Fibers are typically retained on the refiner disks by placing dams between the substantially radially extending bars on the disks. Dams between refiner bars prevent the fibers and stock from being rapidly pumped through the refining region created by the refiner disks.
The use of dams, however, blocks the flow of steam from the refiner disks. When steam is blocked, it can back up and prevent fibers from moving through the refiner disks. If the dams are removed, the steam can blow the stock out of the disks before sufficient refining action has taken place. Refiners are energy intensive pieces of equipment and building a better refiner means a higher throughput with the same or better refining action.
Refiner disks have been fabricated with curved steam exhaust channels which extend radially outwardly and cut across refining grooves and bars. These large-width channels provide a low-resistance path for the escape of steam generated in the refining process, but come only at the sacrifice of a significant portion of refiner bar length, and hence a reduction from the maximum potential refining capacity.
What is needed is a disc refiner which provides improved steam flow with better retention of fibers and increased refining action on the refiner disks.